High affinity mouse-human chimeric Fab against Hepatitis B surface antigen

Figure 1 Schematic representation of the strategy for cloning and expression of the anti-HBs chimeric Fab. The V_H and V_L fragments of 5S hybridoma were fused with human C_H1 and C_L by overlap PCR. The resulting chimeric fragments were cloned in the bi-cistronic phagemid vector pCOMB3H. Both the fragments are under the control of a single LacZ promoter. ompA and pelB are two leader sequences, provided for directing the light chain and Fd fragment to the bacterial periplasm. Two ribosome-binding sites are present in the vector for stable expression of both the fragments. The Fd fragment was cloned upstream to the phage gIII sequence, for surface display of the chimeric Fab. This gIII fragment was removed by digestion with Spe I/Nhe I and after self-ligation of the vector, the Fab fragment was expressed in soluble form.